A new version of June's Download.Ject attack is hitting users through a pair of instant messaging services, planting backdoors on fully-patched Windows XP PCs, and serving victims with a diet of porn ads.

According to Thor Larholm, a senior security researcher at Newport Beach, Calif.-based PivX Solutions, the new attack is probably the work of the same group of hackers who launched the original Download.Ject assault in June.

In that brief-but-high-profile attack, a group of Russian attackers compromised numerous Web servers running Microsoft software, then used a variety of vulnerabilities in the Internet Explorer browser to drop password- and bank account-stealing key loggers on systems whose users had simply surfed to sites hosted on the infected servers.

This attack, said Larholm, is different. "The attacks comes in via AIM or ICQ instant messages, either from random users or users you may know," he said. If the users clicks on the link that reads "My personal home page http://XXXXXXX.X-XXXXXX.XXX/" the server attempts to download the Trojan using several IE vulnerabilities, including Object Data, Ibiza CHM, and MHTML Redirect, he added.

And rather than try to hijack financial data, the object of the new attack appears to be to display porn advertising on end users' machines. "It's still a financial motivation," said Larholm. "And since there's a back door installed, it could be used for other purposes later."

The most noticeable impact of an infection is a modified IE home page and changed search pane. In place of the user's designated home page, the new Download.Ject plants a porn ad page.

The servers delivering the Trojan and backdoor are based in Russia, Uruguay, and the U.S., said Larholm, who said that the U.S.-based server appears to be a compromised machine. The Russian servers, however, appear to be deliberating serving up pages linked in the IMs.

Larholm said that a fully-patched edition of Internet Explorer 6 running on Windows XP SP1 can be compromised by this newest attack, but that machines which have been updated with Windows XP Service Pack 2 (SP2) are safe.

Although there's no definitive proof, Larholm suspects that the same Russian-based HangUP hacker team behind the original Download.Ject attack is also running this show.

"It's not like they use signatures, but there are a lot of similarities, including similar code and even identical file names," he said.

"It doesn't surprise me at all that there's been another Download.Ject attack," added Ken Dunham, the director of malicious code research at iDefense. "There are multiple ways to code attacks against IE's vulnerabilities, and I think we'll continue to see more through the summer and early fall, at least until they prove to be unsuccessful."

well does it detect it or not? I don't want to get it and then have porn popup all over my system. Nothing more horring then comeing back from lunch to a 24" shlongs all over your desktop....well ok maybe a bit more horrid would be to come back from lunch and see a naked guy with a 24" schlong on your office chair becking you to sit on his lap but well that's beyond NOD32 control.